Air preheater for melting furnaces



Jan. l, 1957 A. ARUTUNOFF AIR PREHEATER'FORMELTING FURNACES Filed Oct.7, 1954 INVENTOR ARMA/5 ARUTU/VOFF Illfllllllnll lllllfLlllHM |v I l l ll l l I l l l l l l l Il.

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ATTORNEY Unite States Patent O AIR PREHEATER FR MELTING FURNACES ArmasArutunotf, Bartlesville, Okla., assignor to Reda Pump Company,Bartlesville, Okla., a corporation of Delaware Application October 7,1954, Serial No. 460,934

9 Claims. (Cl. 263-15) This invention relates to melting furnaces of thedirect tired, stack loaded type generally similar to those disclosed inmy former Patents Nos. 2,674,446 and 2,680,609. More particularly, theinvention consists in new and useful improvements in air pre-heaters foruse in connection with furnaces of the type above referred to.

Various means have been employed for preheating the air fed to furnaceblowers, but generally speaking, these pre-heaters have formed anintegral part of the furnace structure and relied upon a heat exchangewith the products of combustion discharged from the furnace.

The primary object of the present invention is to provide a pre-heater,in the form of a substantially rectangular housing adapted to be placedover the lid of the furnace and connected by its own integral duct, tothe blower intake, inlet means being provided on the under side of thehousing to receive the highly heated air radiating from the lid, wherebypre-heated air is drawn into the blower at the burner end of thefurnace.

Another object of the invention is to provide a preheater for directfired melting furnaces, consisting of a very simple sheet metalstructure which may be applied to me furnace without altering thestructure of the latter.

A further object of the invention is to provide a preheater of the typereferred to which will materially lower the melting time of the furnace,reduce the fuel consumption, and minimize element loss or burn-outs.

Still another object of the invention is to provide a preheater whichmay easily be applied to and removed from the furnace for purposes ofrepair and cleaning.

A still further object of the invention is to provide a pre-heater whichsimply rests upon the furnace lid and is so connected to the blowerintake as to permit a hinge action to allow the tilting of thepre-heater from the furnace lid to facilitate access to the furnace.

With the above and other objects in view which will appear as thedescription proceeds, the invention consists in the novel featuresherein set forth, illustrated in the accompanying drawings and moreparticularly pointed out in the appended claims.

Referring to the drawings in which numerals of like character designatesimilar parts throughout the several views,

Figure l is a View in side elevation, showing my improved pre-heater inplace on the lid of a furnace.

Figure 2 is an end View showing the attachment of the pre-heater duct,to the blower air intake.

Figure 3 is a top plan view of the pre-heater.

Figure 4 is an enlarged sectional detail, taken on line 4 4 of Figure 3,showing the mounting bracket, and

Figure 5 is a sectional view taken on line 5 5 of Figure 3.

In the drawings, referring to Figures l and 2, 6 generally representsthe body portion of a stack-loaded, directtired melting furnace of theoscillatory type such as described in my said former patents. The mainshell of the furnace body is formed of vertical sheet metal side2,776,136 Patented Jan. l, 1957 lCC walls 7 and end walls 8, all weldedor otherwise jointed together and to the bottom (not shown) to form aboxlike container. The top edges of the vertical walls 7 and 8 areprovided with outwardly directed flanges or angle irons 9 whichpreferably extend entirely around the top of the furnace shell toaccommodate complementary flanges 10 on the furnace stack l1 whichoverlies one end of the furnace body, and serving also to attach themain furnace closure or lid generally indicated by the numeral 12.

As explained in my said former patents, the furnace shell is lined withrefractory brick arranged to provide a trough-like receptacle oraccumulator, one end of which communicates with the overlying stackshell 11 which is likewise lined with refractory brick within its threexed walls. The refractory lining of the furnace proper may extendslightly above the upper extremities of the shell walls 7 8 as shown at13, to directly support the overall lid structure l2. The lid 12.consists of horizontal slabs 14 of refractory material arranged tobridge the top opening of the furnace proper, their opposite extremitiesbeing embraced by transversely extending channel members l5, preferablyarranged in pairs overlying each of the lid slabs le. The opposite endsof each of the cross channels 15 is bent downwardly and outwardly as atlo to overlie the flanges 9 on the upper edges of the furnace shellwalls. When in place, the ends 16 of the cross channels are normallyvertically spaced from the flanges 9 so as to allow for tightening whenbolts 17 are inserted in registering openings in the ends 16 and flanges9 respectively.

As is the case of my said former patents, the stack 11 has three linedshell walls which border that end of the furnace, the stack being closedon the furnace side by removable closure slabs t3 of refractorymaterial. These are held in place by channels i9 similar to channels l5and provided with securing bolts 2li at each end, engaging verticalanges 21 on the edges of the side walls 11 of the stack.

At the opposite end, the furnace is provided with a burner blowerassembly 22, mounted on the furnace end wall by a bracket 23 and havingan air fuel mixture discharge conduit 2li leading to the interior of thefurnace and terminating in a burner nozzle (not shown). The blower isprovided with the usual air intake housing Z5, generally frustoconicalin shape and provided at its aring inlet end with a rotatable damper(not shown) having a radially projecting control arm 27.

A fuel supply line 23 is connected to the burner blower assembly by afeed extension 29 leading to the axis of the blower 22, and the furnacebody may be mounted for oscillation by any conventional means, themounting 26 shown in the drawings, being generally similar to thosedescribed in my said former patents.

The description thus far has been directed to the furnace structure soas to clarify the environment for which my pre-heater was primarilydesigned. It will be understood however, that the basic principle of thepresent invention may be employed with furnaces of different specificconstructions which lend themselves to this type of pre-heating.

Turning now to the pre-heater itself, it will be seen from Figures l to3 that it comprises a substantially rectangular box-like housing Silpreferably formed of sheet metal. The housing has a top Wall 31 and sidewalls 32 and 33 and is of sufficient transverse and longitudinaldimensions to substantially overlie the furnace lid i2 as willhereinafter appear. The bottom wall 34 of the housing 30 is providedwith an enlarged rectangular opening 35 shown in dotted lines in Figure3 and of suflicient size to expose the major portion of the interior ofthe housing to the heat radiated from the furnace lid 12. The end of thehousing adjacent the stack 11 is open and spaced laterally from the lidclosure 18 to permit manipulation of the lid slabs. However, thebounding edges of said opening may be bent inwardly to form reinforcingflanges 36 as shown in Figure l.

The opposite end wall 37 of the housing is preferably angularly disposedand terminates at one side of the housing in an integral duct 33 formedby the combined extensions of the top, bottom and side walls of thehousing. This duct is turned downwardly at its end which carries ahorizontally disposed, cylindrical extension 39, means of which the ductis connected to the air inlet opening of the blower 22. Preferably, thecylindrical extension 39 is formed with upper and lower sections flangedas at 40 and secured together by bolts or the like 41.

The diameter of the cylindrical extension 39 permits it to fit over andtightly embrace the flaring air inlet housing 25 of the blower 22 whenthe bolts 41 are secured and the periphery of its upper section isprovided with a transverse slot 42 to accommodate the damper control arm27. The fuel feed extension 29 is accommodated by a suitable opening 43in the end wall of the cylindrical extension 39 and passes axiallythrough the latter for connection to the burner element of blower 22.

The entire housing 3l) normally rests upon top edges of the channels 15of the lid 12 and is pivotally supported by its duct and cylindricalextension 39 which ts around the blower intake housing. However, as anadded measure of support, the cylindrical extension 39 is preferablyprovided with a transverse bracket member 455 which may be welded to theinner walls of the extension 39 and is provided centrally with anarcuate recess 45 adapted to t over the fuel feed extension 29 as shownin detail in Figure 4. A substantially U-shaped yoke lo underlies thefeed extension 2%? and is secured to the bracket di by means of screwsor bolts 7. This bracket arrangement, together with the pivotalrelationship of the cylindrical extension 39 on the blower intakehousing 25, permits the pre-heater housing 3. to be bodily tilted incounter-clockwise direction from the position shown in Figure l. Furtherpivotal support can be afforded by engagement of the outer end of feedextension 29, by the concentric opening i3 in the side wall of the duct38 which closes the end of thc Cylinder 39. In other words, athree-point pivotal support is provided by the air inlet housing .5, thebracket and the opening 43.

In order to add rigidity to the housing fill, I preferably provide aseries of longitudinally exterd ng, laterallyspaced angle irons [i3which may be welded to the under side of the top wall 3l. Also ifdesired, one transverse angle iron 49 may be provided adjacent the inletend of the housing to prevent sagging of the top wall.

In operation, the housing receives its air supply through the bottomopening E5 and the end opening 3o, the air having been pre-heated by theradiated temperature from the furnace closure slabs ld and the stackclosure slabs 1S which heat would otherwise have been wasted anddissipated in the surrounding atmosphere. The bottom wall 34 of thehousing, being supported on the top horizontal edges of the crosschannels 15, is thereby spaced vertically from the top surfaces of theslabs Thus, hot air may enter the bottom opening of the housing allalong the lid and between the franges of the channels 15. The pre-heaterraises the temperature of the .air at the blower intake 25 toapproximately 200 F. which of course, reduces the amount of oxygen in agiven volume of air pumped into the furnace. However, blowers of thetype employed with these furnaces are of sufiicient capacity to morethan compensate for this reduction in oxygen. Experiments have shownthat melting time on gray iron (i. e. from charged to pour) is reducedby approximately l() percent, or, conversely, the metal temperature willbe higher for the same length of time Fuel consumption is actuallyreduced by more than this amount, due to less time as well as less airand consequently less fuel going into the furnace. Losses of elements(carbon and silicon) are greatly reduced, due to less time exposed and,because the heated air tends to mix better with the fuel, gives not onlybetter combustion but less free oxygen over the bath.

The same benefits would obviously be derived in connection with brassand bronze melting. In fact, even greater benets might be expected fromthe standpoint of oxidation of white metals from red brasses. Obviouslyany reduction in melting rates is always advantageous as is the loweringof fuel costs.

It has beenrny experience that approximate reduction in melting timehave been on the order of 15 percent; fuel savings on the order of 20percent; and carbon and silicon losses have been reduced to nil onordinary gray iron alloys. On exceptionally high carbon metals, such asused for ductile iron, carbon losses are reduced to a limit that causesno concern in production. In fact, by use of an admixture of oil withgas fuel, carbon can be maintained at any desired level. In lower carbonirons (below about 3.10) the level can actually be increased.

From the foregoing it is believed that my invention may be readilyunderstood by those skilled in the art without further description, itbeing borne in mind that numerous changes may be made in the detailsdisclosed without departing from the spirit of the invention as setforth in the following claims.

I claim:

l. In a melting furnace having a melting chamber, a burner-blowerassembly at one end and a removable lid bridging the top of saidchamber; an air pre-heater for said burner-blower, comprising asubstantially box-like housing overlying said lid with its underside invertically spaced relation and supported thereby, air inlet means on theunderside of said housing directly exposed to the top surface of saidlid, a duct at one end of said housing, and means connecting said ductto the air inlet of said burnerblower assembly.

2. In a melting furnace having a melting chamber, a vertical loadingstack at one end of said chamber, a burner-blower assembly at the otherend of said chamber, a removable lid bridging the top of said chamber,and a removable closure for the vertical wall of said stack facing saidchamber; an air pre-heater for said burnerblower, comprising `arelatively shallow box-like housing overlying said lid with itsunderside in vertically spaced relation and supported thereby, openingson the underside and the end of said housing adjacent said stack, toreceive heated air drawn across the hot surfaces of said lid and stackclosure, the other end of said housing terminating in a duct, and meansconnecting said duct to the air inlet of said burner-blower assembly.

3. In a melting furnace having a melting chamber, a burner-blowerassembly at one end and a removable lid bridging the top of saidchamber; an air pre-heater for said burner-blower, comprising asubstantially box-like housing of sheet metal, overlying said lid withits underside in vertically spaced relation and supported thereby, .airinlet means on the underside of said housing directly exposed to the topsurface of said lid, one end of said housing terminating in a duct, andmeans connecting said duct to the air inlet of said burner-blowerassembly.

4. A device as claimed in claim 3, wherein said housing is pivotallymounted with respect to said lid.

5. In a melting furnace having a melting chamber, a vertical loadingstack at one end of said chamber, a burner-blower assembly at the otherend of said chamber, a removable lid bridging the top of said chamberand a removable closure for the vertical wall of said stack facing saidchamber; an air pre-heater for said burnerblower, comprising arelatively shallow box-like housing of sheet metal, overlying said lidwith its underside in vertically spaced relation and supported thereby,openings on the underside and the end `of said housing adjacent saidstack, to receive heated air drawn across the hot surfaces of said lidand closure, the other end of said lhousing terminating in a duct, andmeans connecting said duct to the inlet of said burner-blower assembly.

6. Apparatus as claimed in claim 5, wherein said housing is pivotallymounted with respect to said lid.

7. Apparatus as claimed in claim 5, wherein said duct is connected tosaid burner-blower assembly by a cylindrical extension coaxial with thelatter, and means supporting said extension for rotary movement aboutthe axis of said burner-blower.

8. In a melting furnace having a melting chamber, a burner-blowerassem'bly including an air inlet ange, at one end of said chamber, ahorizontal fuel conduit leading to the burner coaxially of said inletange, and a removable lid bridging Ithe top of said chamber; an airpre-heater for said burner-blower, comprising a substantially box-likehousing overlying said lid with i-ts underside in vertically spacedrelation and supported thereby, air inlet means on the underside of saidhousing directly exposed to the top surface of said lid, a downwardlydirected duct at one end of said housing overhanging the burner-blowerend of said chamber, a substantially cylindrical extension at the lowerextremity of said duct, projecting horizontally therefrom with its freeend embracing said air inlet flange, and means supporting said extensionand housing for rotation about the horizontal axis of said ange.

9. Apparatus as claimed in claim 8, wherein said extension rotatablyembraces the periphery of said flange.

References Cited in the le of this patent UNITED STATES PATENTS1,719,684 Besta July 2, 1929 1,875,169 Sklenar et al. Aug. 30, 19322,225,166 Erby Dec. 17, 1940 FOREIGN PATENTS 511,572 Great Britain Aug.21, 1939

